Vapor deposition of metal oxides, silicates and phosphates, and silicon dioxide

ABSTRACT

Metal silicates or phosphates are deposited on a heated substrate by the reaction of vapors of alkoxysilanols or alkylphosphates along with reactive metal amides, alkyls or alkoxides. For example, vapors of tris(tert-butoxy)silanol react with vapors of tetrakis(ethylmethylamido)hafnium to deposit hafnium silicate on surfaces heated to 300° C. The product film has a very uniform stoichiometry throughout the reactor. Similarly, vapors of diisopropylphosphate react with vapors of lithium bis(ethyldimethylsilyl)amide to deposit lithium phosphate films on substrates heated to 250° C. Supplying the vapors in alternating pulses produces these same compositions with a very uniform distribution of thickness and excellent step coverage.

RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S. patentapplication Ser. No. 11/199,032, now issued as U.S. Pat. No. 7,507,848,filed on Aug. 8, 2005, which claims the benefit of the filing date ofU.S. patent application Ser. No. 10/381,628, now issued as U.S. Pat. No.6,969,539, which is the national stage application of PCT ApplicationNo. US01/30507, filed on Sep. 28, 2001, which claims the benefit of thefiling date of U.S. Provisional Patent Application Nos. 60/236,283,filed Sep. 28, 2000 and 60/253,917, filed on Nov. 29, 2000, the contentsof which are hereby incorporated by reference herein in theirentireties.

STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

This invention was made with the support of the United States governmentunder National Science Foundation Grant No. ECS-9975504. The UnitedStates has certain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel reagents for use in thin film depositionprocesses such as chemical vapor deposition (CVD) and atomic layerdeposition (ALD). These reagents can be used for deposition of materialscontaining silicon and/or phosphorus along with metals and/or oxygen,commonly called metal oxides, silicates or metal phosphates, or silicondioxide.

2. Description of the Related Art

Chemical vapor deposition (CVD) is a widely-used process for formingsolid materials, such as coatings or powders, from reactants in thevapor phase. Comprehensive reviews of CVD processes have been givenrecently in CVD of Nonmetals, W. S. Rees, Jr., Editor, VCH Publishers,Weinheim, Germany, 1996; CVD of Compound Semiconductors, A. C. Jones andP. O'Brien, VCH, 1996; and The Chemistry of Metal CVD, T. Kodas and M.Hampden-Smith, Editors, VCH, 1994.

In CVD processes, a reactant vapor or vapor mixture is brought intocontact with a heated surface on which a thin film is deposited. In arelated form of CVD, two reactant vapors are alternately exposed to theheated surface. This form of CVD is often called atomic layer deposition(ALD). For suitable reactants, ALD can provide improved step coverageand thickness uniformity compared to CVD with mixed vapors. For a reviewof ALD, see the paper by Mikko Ritala in Applied Surface Science, volume112, pages 223-230 (1997).

Coatings of metal silicates have many applications or potentialapplications. For example, silicates of zirconium, hafnium, yttrium orlanthanum are being considered as potential replacements for silicondioxide in gate insulators in silicon semiconductor technology. See, forexample, A. Kingon et al., Nature, volume 406, pages 1032-1038 (2000).In Science, (volume 288, pages 319 to 321 (2000)), Ritala et al. reportthe use of the sequential ALD reaction of metal chlorides and siliconalkoxides to produce metal silicates, including zirconium silicate.However, this reaction deposits films containing residual chlorine,which can be deleterious to the properties of the film or to itsadhesion to substrates or subsequent coatings. The chlorine in theprecursors can also corrode metal substrates or the apparatus used forthe deposition. Thus it would be advantageous to have chlorine-freeprecursors for CVD or ALD of metal silicates or oxides.

ALD of silicon dioxide has been achieved by Klaus et al., U.S. Pat. No.6,090,442 (2000), but the deposition rate is very slow and the substratetemperature is limited to values near room temperature.

Lithium phosphate is a material of current interest as a lithium ionconductor in lithium batteries. Currently there is no known process forCVD or ALD of lithium phosphate.

SUMMARY OF THE INVENTION

A principal feature of the present invention includes volatile chemicalprecursors with reactivity adapted for CVD or ALD of metal silicates,phosphates or oxides.

An advantage of these chemical precursors is that they do not containchlorine, and leave no chlorine residue during a process for the CVD orALD of metal silicates, phosphates or oxides.

A related feature of the present invention is the deposition of metalsilicates under conditions that produce a sharp interface betweensilicon substrates and the deposited metal silicate.

An advantage of the process is that it permits deposition of materialscontaining metal silicates or phosphates by a CVD process in which allthe reactants may be mixed homogeneously before delivery to the heatedsurface of the substrate.

An additional advantage of the process is the vapor deposition of metalsilicates or phosphates with relatively fixed ratio of metal to siliconover a range of conditions such as concentrations of reactants andposition of the substrate inside the reactor.

Another advantage of the invention is its ability to make conformalcoatings over substrates with narrow holes, trenches or otherstructures. This ability is commonly known as good step coverage.

Another feature of the present invention is the preparation of materialcomprising lithium phosphate.

An advantage of the invention is that the reactants are stable andrelatively nonhazardous.

Another feature of the invention includes a chemical vapor deposition oratomic layer deposition process for metal oxides or mixtures of metaloxides.

A further feature of the invention includes process for atomic layerdeposition of silicon dioxide.

One particular feature of the present invention includes a process fordepositing oxides or silicates of zirconium, hafnium, yttrium and/orlanthanum having high dielectric constants of use as gate insulators ortrench capacitors in microelectronic devices.

Another particular feature of the present invention includes a processfor depositing silicon dioxide or metal silicates having useful opticalproperties, such as in planar waveguides andmultiplexers/demultiplexers, and in optical interference filters.

An additional feature of the present invention includes a process fordepositing lithium phosphate coatings allowing rapid diffusion oflithium for use as separators in batteries or electrochromic devices.

Other features and advantages of the invention will be obvious to thoseskilled in the art on reading the instant invention.

In one aspect of the invention vapors of alkoxysilanols are reacted withthe vapors of suitably reactive metal or metalloid compounds, such asmetal or metalloid alkylamides, alkyls or cyclopentadienyls, to formmetal silicates. The reaction may be carried out in a manner to formfilms.

In at least some embodiments, tris(alkoxy)silanol compounds have thegeneral formula 1, in which R^(n) represents hydrogen, alkyl groups,fluoroalkyl groups or alkyl groups substituted with other atoms orgroups, preferably selected to enhance the volatility of the compound,where R^(n) is any one of R¹ through R^(n). The R^(n) may be the same ordifferent from each other.

In at least some embodiments methyl groups are selected for each of theR^(n) in the general formula 1 given above one obtains a highlypreferred compound tris(tert-butoxy)silanol 2, which may be written morecompactly as (^(t)BuO)₃SiOH.

Another compound of the invention is tris(tert-pentyloxy)silanol, alsoknown as tris(tert-amyloxy)silanol 3, which may be written morecompactly as (^(t)AmO)₃SiOH.

In at least some embodiments of the invention Di(alkoxy)silanediols suchas (⁴BuO)₂Si(OH)₂ can also be used, although they are less stable thantris(alkoxy)silanol compounds in at least some applications.Di(alkoxy)silanediol compounds having the general formula 4 may be usedaccording to the invention, where R^(n), represents hydrogen, alkylgroups, fluoroalkyl groups or alkyl groups substituted by other atoms orgroups, preferably selected to enhance volatility and stability, and maybe the same or different for any R^(n), and R^(n) is any of R¹ throughR⁶ may be the same or different.

In at least some embodiments, the groups R₁ for the general formula 1 orR¹-R⁶ for the general formula 4 may be selected from the groupconsisting of hydrogen, methyl, ethyl, n-propyl and isopropyl groups.

In the foregoing compounds, it is also understood that the alkyl groupsR¹ through R⁹ for general formula or R¹ through R⁶ for general formula 4may be a hydrocarbon having some degrees of unsaturation, e.g., aryl,alkenyl or alkynyl groups.

In at least some embodiments, metal compounds include those that reactreadily with the slightly acidic protons in silanols. These acidicprotons are the ones attached directly to oxygen in the silanol. Metalcompounds that generally react with these acidic protons include mostmetal alkyls and other organometallic compounds, metal alkylamides, andsome metal alkoxides. The reactivity of any particular compound can beestablished readily by mixing it with an alkoxysilanol and analyzing themixture for products by techniques such as nuclear magnetic resonance(NMR). We have found that compounds that are known to react with wateralso generally react with alkoxysilanols.

We have also discovered that the stoichiometry of the deposited metalsilicates can be controlled. The silicon/metal ratio may be decreased byreplacing some or all of the silanol with water or an alcohol.Conversely, the silicon/metal ratio may be increased by replacing someor all of the metal source by a suitably reactive silicon-containingcompound such as a silicon amide or a silylene. By these methods thecomposition of the deposited material may be chosen to be anycomposition from pure metal oxide to pure silicon dioxide or any desiredsilicon/metal ratio in between. The stoichiometry may even be variedduring the course of one deposition. For example, in the deposition of agate insulator for a silicon semiconductor device, it may be desirableto begin the deposition with a silicon-rich layer close to the siliconsurface in order to improve the electrical properties of the interface,followed by a metal-rich layer with higher dielectric constant.

In another aspect of the invention, vapors of bis(alkyl)phosphates arereacted with the vapors of reactive metal compounds, such as metalalkylamides, metal alkyls, metal cyclopentadienides or metal alkoxides,to form metal phosphates. The reaction may be carried out in a way thatforms films.

In at least some embodiments of the invention, phosphorus-containingprecursors include bis(alkyl)phosphates 5 in which R^(n), representshydrogen, alkyl groups, fluoroalkyl groups or alkyl groups, substitutedwith other atoms or groups where R^(n) may be any of R¹ through R⁶. TheR^(n) may be the same or different from each other.

In at least one embodiment, the phosphorus precursor isdiisopropylphosphate, represented by the formula 6.

It is also possible to control the stoichiometry of the metalphosphates. The phosphorus/metal ratio may be decreased by replacingsome or all of the bis(alkyl)phosphate with water or an alcohol.Conversely, the phosphorus/metal ratio may be increased by replacingsome or all of the metal source by a suitably reactive phosphorussource. By these methods, the composition of the deposited material maybe varied from pure metal oxide to pure phosphorus oxide or any desiredphosphorus/metal ratio.

In at least some embodiments, the groups R¹-R⁶ for the general formula 5may be selected from the group consisting of hydrogen, methyl, ethyl,n-propyl or isopropyl groups. In the foregoing compounds, it is alsounderstood that the alkyl groups R¹ through R⁹ for general formula 1 orR¹ through R⁶ for general formula 4 may be a hydrocarbon having somedegrees of unsaturation, e.g., aryl, alkenyl—alkynyl groups.

In another aspect of the invention, a process for preparing a materialcomprising silicon includes exposing a substrate to one or more vaporschosen from the group consisting of alkoxysilanols, alkoxysilanediolsand silylenes. In at least some embodiments, the silylene is thecompound described by the formula

where R is an alkyl group, or R is tert-butyl.

In one aspect of the invention, a process for forming a materialincluding phosphorus includes exposing a substrate to one or more vaporschosen from the group consisting of bis(alkyl)phosphates,phosphorus(III) oxide and white phosphorus.

In another aspect of the invention, a process is provided for preparingoxygen-containing materials including exposing a substrate to one ormore vapors chosen from the group consisting of arene hydrates, such asbenzene hydrate, naphthalene hydrate, or a substituted benzene hydrateor a substituted naphthalene hydrate.

In another aspect of the invention, a process for forming a metal oxideis provided including exposing a heated surface alternately to the vaporof one or more metal amides and then to the vapors of water or analcohol.

In at least some embodiments, the alcohol is an arene hydrate, or in atleast some embodiments, the metal amide or amides are chosen from Table1.

In another aspect of the invention, a process for forming materialincluding oxygen and one or more metals is provided by exposing asurface alternately to the vapor of one or more organometallic compoundsand to the vapor of an arene hydrate.

In at least one embodiment, the organometallic compounds are chosen fromTable 2.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects, features, and advantages of the present invention canbe more fully appreciated with reference to the following detaileddescription of the invention when considered in connection with thefollowing drawings. The drawings are presented for the purpose ofillustration only are not intended to be limiting of the invention, inwhich:

FIG. 1 is a cross-sectional illustration of an atomic deposition layerapparatus used in the practice of at least one embodiment of theinvention;

FIG. 2 is a cross-sectional illustration of an atomic deposition layerapparatus used in the practice of at least one embodiment of theinvention; and

FIG. 3 is a cross-sectional scanning electron micrograph of holes in asilicon wafer uniformly coated with hafnium dioxide using one embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION

1. Metal Silicates and Silicon Dioxide.

The present invention provides a method for preparing metal silicates ofvarying metal and silicon content. The method involves the reaction of avapor of an alkoxysilanol or alkoxysilanediol with a vapor of one ormore metal or metalloid compounds. The compound may be formed as apowder or as a film on a substrate, and in some embodiments, on a heatedsubstrate. The compound may be formed on a substrate by mixing thevapors of the alkoxysilanol or alkoxysilanediol and the metal ormetalloid compound prior to deposition on a substrate. In at least someembodiments, a substrate is alternately exposed to a alkoxysilanol oralkoxysilanediol vapor and a vapor of one or more of a metal ormetalloid compound.

Silanol and silanediol reactants are commercially available or may beprepared using conventional or known techniques. Silicon precursor,tris(tert-butoxy)silanol, is commercially available from AldrichChemical Company (Milwaukee, Wis.) and Gelest, Inc. (Tullytown, Pa.).Tris(tert-butoxy)silanol may be prepared as follows. Firsttris(tert-butoxy)chlorosilane is made by either of the following tworeactions:SiCl₄+3^(t)BuOH→(^(t)BuO)₃SiCl+3HCl  (1)SiCl₄+3NaO^(t)Bu→(^(t)BuO)₃SiCl+3NaCl  (2)The tris(tert-butoxy)chlorosilane is then hydrolyzed according to thereaction(^(t)BuO)₃SiCl+H₂O→(^(t)BuO)₃SiOH+HCl  (3)

See, Backer et al., Rec. Tray. Chim., volume 61, page 500 (1942). Thiscompound is a solid at room temperature and melts at about 66° C. Itsublimes at room temperature at a low pressure of about 10⁻⁴ Torr, andcan be distilled at a temperature of about 104° C. at a pressure of 20Torr. It is highly soluble in organic solvents such as mesitylene ortetradecane, so that its vapors can be formed conveniently by flashvaporization of its solution.

Other tris(tert-alkoxy)silanols may be prepared by similar reactions, bysubstituting other tertiary alcohols, such as tert-pentyl alcohol (alsoknown as tert-amyl alcohol), for tert-butanol.Tris(tert-amyloxy)silanol, (^(t)AmO)₃SiOH, is a liquid at roomtemperature, so its vapors can be formed conveniently by flashvaporization of the neat liquid. It has a vapor pressure of about 2 Torrat 96° C. It is commercially available from Aldrich Chemical Company.

Silanols and silanediols may be reacted with a metal source to obtain ametal silicate. The metal source may contain one or more metals and theresultant metal silicate may contain one or more metals. In at leastsome embodiments, metal compounds include those that react readily withthe slightly acidic protons in silanols. These acidic protons are theones attached directly to oxygen in the silanol. Metal compounds thatgenerally react with these acidic protons include most metal alkyls andother organometallic compounds, metal alkylamides, and some metalalkoxides. The reactivity of any particular compound can be establishedreadily by mixing it with an alkoxysilanol and analyzing the mixture forproducts by techniques such as nuclear magnetic resonance (NMR). We havefound that compounds that are known to react with water also generallyreact with alkoxysilanols.

The reaction is carried out in the vapor state and may be carried outusing CVD or ALD techniques. As is discussed in greater detail below,ALD provides control over the deposition process and is suitable for usein a wide range of reaction conditions and reactant reactivity.

The silicon/metal ratio may be increased by replacing some or all of themetal precursor by a suitably reactive silicon compound. Silicon halidessuch as silicon tetrachloride, SiCl₄, may be used to increase thesilicon content, but they may leave chloride as an impurity in theproduct, and their reactions may be slower than desired. Silicon amidessuch as tetraisocyanatosilane, tetrakis(dimethylamido)silane ortris(dimethylamido)silane avoid the halogen contamination. However,their deposition rates may also be slower than desired. Silylenes aremore rapidly reactive. For example, the thermally stable silylene 7

where R is an alkyl group or, in at least some embodiments, istert-butyl, can be used as a rapidly reacting silicon source in place ofpart or all of the metal source, in order to increase the silicon/metalratio.

In at least some embodiments, pure silicon dioxide may be prepared. Inan ALD system, a pulse of silylene is followed by a pulse of oxygen gas,in order to fully oxidize the silylene after it has reacted with thesurface. Pure silicon dioxide can be deposited rapidly by repeating thepulse sequence of silylene and oxygen.

2. Metal Phosphate and Phosphorus Oxide.

The present invention provides a method for preparing metal phosphatesof varying metal and phosphorus content. The method involves thereaction of a vapor of an bis(alkyl)phosphate with a vapor of one ormore metal or metalloid compounds. The compound may be formed as apowder or as a film on a substrate, and in some embodiments, on a heatedsubstrate. The compound may be formed on a substrate by mixing thevapors of the bis(alkyl)phosphate and the metal or metalloid compoundprior to deposition on a substrate. In at least some embodiments, asubstrate is alternately exposed to a bis(alkyl)phosphate vapor and avapor of one or more of a metal or metalloid compound.

Bis(alkyl) phosphate reactants are commercially available or may beprepared using conventional or known techniques. Phosphorus precursor,diethylphosphate, is commercially available from a number of chemicalcompanies, including Fisher Scientific (Pittsburgh, Pa.) and Pfaltz andBauer (Waterbury, Conn.). Diethylphosphate may be prepared by the airoxidation of phosphinic acid in ethanol, catalyzed by copper chloride:₂P(O)OH+2EtOH+O₂→(EtO)₂P(O)OH+2H₂O  (4)See, Y. Okamoto, T. Kusano and S. Takamuku, Phosphorus, Sulfur andSilicon, volume 55, pages 195-200 (1991).

An alternative reaction sequence is shown for diisopropylphosphate andmay be used for other precursor compounds by appropriate substitutionsfor isopropanol.PCl₃+3^(i)PrOH→(iPrO)₂P(O)H+^(i)PrCl+2HCl  (5)(^(i)PrO)₂P(O)H+SO₂Cl₂→(^(i)PrO)₂P(O)Cl+HCl+SO₂  (6)(^(i)PrO)₂P(O)Cl+H₂O→(^(i)PrO)₂P(O)OH+HCl  (7)See, Mclvor et al., Canadian J. Chemistry, volume 34, pages 1825 and1827.

Diisopropylphosphate may also be prepared by first forming its potassiumsalt by the following two reactions:PCl₃+3^(i)PrOH→(^(i)PrO)₂P(O)H+^(i)PrCl+2HCl  (8)2(^(i)PrO)₂P(O)H+KMnO₄+KHCO₃→2(^(i)PrO)₂P(O)OK+MnO₂  (9)See, A. Zwierak and M. Kluba, Tetrahedron, volume 27, pages 3163 to 3170(1971). The analogous sodium salt may be prepared by the following tworeactions:POCl₃+3^(i)PrOH→(^(i)PrO)₃P═O+3HCl  (10)(^(i)PrO)₃P═O+NaOH→(^(i)PrO)₂P(O)ONa+^(i)PrOH  (11)The precursor diisopropylphosphate may then be liberated from its alkalisalt by reaction with hydrochloric acid:(^(i)PrO)₂P(O)OM+HCl→(^(i)PrO)₂P(O)OH+MCl,M=Na,K  (12)

The above bis(alkyl)phosphates react with a wide range of metalcompounds to form metal phosphates. Metal compounds that generally reactwith the acid phosphate protons include most metal alkyls and otherorganometallic compounds, metal alkylamides, and some metal alkoxides.The reactivity of any particular compound can be established readily bymixing it with a bis(alkyl)phosphate and analyzing the mixture forproducts by techniques such as nuclear magnetic resonance (NMR).

The reaction is carried out in the vapor state and may be carried outusing CVD or ALD techniques. As is discussed in greater detail below,ALD provides control over the deposition process and is suitable for usein a wide range of reaction conditions and reactant reactivity.

The phosphorus/metal ratio may be increased by replacing some or all ofthe metal precursor by a suitably reactive phosphorus compound.Phosphorus halides such as phosphorus trichloride, PCl₃, phosphoruspentachloride, PCl₅, or phosphorus oxychloride, POCl₃, may be used, butsome halogen impurity may be included in the film. Phosphorusalkylamides such as hexamethylphosphorus triamide, (Me₂N)₃P,hexamethylphosphorimidic triamide, (Me₂N)₃P═NH, orhexamethylphosphoramide, (Me₂N)₃PO, avoid the halogen contamination, buttheir reactions may be slow. White phosphorus, P₄, and phosphorus(III)oxide, P₄O₆, are more quickly reactive and can be used to increase thephosphorus/metal ratio in an ALD process. Doses of white phosphorus orphosphorus(III) oxide generally are followed by a pulse of oxygen inorder to form fully oxidized films.

The phosphorus/metal ratio of material made by ALD may be decreased byreplacing some of the phosphorus doses by doses of water or alcohol.

3. Metal Amides, Metal Alkyls and Metal Alkoxides.

In at least some embodiments, metal or metalloid amides are useful inthe practice of this invention. Some examples are given in Table 1, aswell as a commercial source and/or literature references for theirsynthesis. The metalloids referred to in Table 1 are boron, silicon andarsenic.

TABLE 1 Some Volatile Metal or Metalloid Amides Melt. Pt. Vapor Press.Compound ° C. ° C./Torr Reference and/or commercial sourceAl(N(SiMe₃)₂)₃ 188 Wannagat, J. Organomet. Chem. 33, 1 (1971) Al₂(NEt₂)₆liquid Barry & Gordon, 2000 Al₂(NEtMe)₆ liquid  100/0.25 Barry & Gordon,2000 Al(N^(i)Pr₂)₃ 56-59 Brothers, Organometallics 13, 2792 (1994)Al₂(NMe₂)₆ 88-89  90/0.1 Ruff, JACS 83, 2835 (1961)Al(N(Et)CH₂CH₂NMe₂)(NMe₂)₂ liquid 65-70/0.3 Barry, Gordon & Wagner, Mat.Res. Soc. Symp. Proc. 606, 83-89 (2000) As(NMe₂)₃ −53 55/10 Cowley, JACS95, 6505 (1973) As(N(Me)(SiMe₃))₃ 11-13 67-70/0.1 Birkofer & Ritter,Chem. Ber. 93, 424 (1960) B(NMe₂)₃ −10 39/10 Abel et al., J. Chem. Soc.1964, 5584 B(NEt₂)₃ 95/11 Abel & Armitage J. Organomet. Chem. 5, 326(1966) Ba(N(SiMe₃)₂)₂ >150 Westerhauser, Inorg. Chem. 30, 96 (1991)Be(NMe₂)₂ 88-90 175/760 Anderson, JACS 74, 1421 (1952) Be(N(SiMe₃)₂)₂−5, liquid 110/3  Clark & Haaland, Chem. Commun., 1969, 912 Be(TMPD)₂−10, liquid   106/0.001 Noeth & Schlosser, Inorg. Chem. 22, 2700 (1983)Bi(N(SiMe₃)₂)₃ 90 Lappert, J. Chem. Soc, Dalton, 2428(1980)Bi(N(Me)(SiMe₃))₃ 90-92/0.1 Birkofer & Ritter, Chem. Ber. 93, 424 (1960)Ca(N(SiMe₃)₂)₂ >120 Lappert, J. Chem. Soc, Chem. Comm., 1141(1990)Cd(N(SiMe₃)₂)₂ liquid Burger, Wannagat, J. Organomet. Chem. 3, 11(1965)Cd(N^(t)BuSiMe₃)₂ Fisher & Alyea, Polyhedron 3, 509 (1984) Cd(TMPD)₂Fisher & Alyea, Polyhedron 3, 509 (1984) Ce(N(SiMe₃)₂)₃ 95-100/10⁻⁴Bradley, J. Chem. Soc, Dalton 1973, 1021 Ce(N^(i)Pr₂)₃ Angew. Chem.,Int. Ed. Engl. 36, 2480(1997) Co(N(SiBuMe₂)₂)₂ liquid   146/0.085Broomhall-Dillard & Gordon, 1999 Co(N(SiEtMe₂)₂)₂ liquid  106/0.05Broomhall-Dillard & Gordon, 1999 Co(N(SiMe₃)₂)₂ >70 50-70/0.01 Chisholm,CVD 1, 49 (1995) Co(N(SiMe₃)₂)₃ 86-88 Power, JACS 11, 8044 (1989)Co(N(SiPrMe₂)₂)₂ liquid  106/0.05 Broomhall-Dillard & Gordon, 1999Cr(N(SiMe₃)₂)₃ 120   80/0.005 Bradley, J. Chem. Soc, Dalton 1972, 1580Cr(NEt₂)₄ liquid 40-60/10⁻³ Bradley, Proc. Chem. Soc, London 1963, 305Cr(N^(i)Pr₂)₃ Bradley & Chisholm, Chem. Comm. 1968, 495 Cr(NMe₂)₄Bradley, J. Chem. Soc. A, 1971, 1433 Cu₄(N(SiMe₃)₂)₄ >180(d.) 160/0.1 Chisholm, CVD 1, 49 (1995) Er(N(SiMe₃)₂)₃ 150-180 Wolczanski, Inorg.Chem. 31, 1311 (1992) Eu(N(SiMe₃)₂)₃ 160-162 82-84/10⁻⁴ Bradley, Chem.Comm. 1972, 349 Fe(N(SiBuMe₂)₂)₂ liquid 130/0.2 Broomhall-Dillard &Gordon, 1999 Fe(N(SiMe₃)₂)₂ 5, liquid 80-90/0.01 Chisholm, CVD 1, 49(1995) Fe(N(SiMe₃)₂)₃ >80   80/0.005 Bradley, J. Chem. Soc, Dalton 1972,1580 Ga(NMe₂)₃ 91  125/0.01 Chemat Catalog, Northridge, CA Ga(NEt₂)₃Chemat Catalog, Northridge, CA Ga(N(SiMe₃)₂)₃ 187 Wannagat, J.Organomet. Chem. 33, 1 (1971) Ga(N^(t)BuSiMe₃)₃ 174-176 Cowley, Inorg.Chem. 33, 3251 (1994) Ga(TMPD)₃ 130-132 Cowley, Inorg. Chem. 33, 3251(1994) Ga(N(Me)CH₂CH₂NMe₂)(NMe₂)₂ liquid 48-55/0.18 Barry, Gordon &Wagner, Mat. Res. Soc. Symp. Proc. 606, 83-89 (2000) Gd(N(SiMe₃)₂)₃160-163 80-83/10⁻⁴ Bradley, Chem. Comm. 1972, 349 Ge(N(SiMe₃)₂)₂ 33  60/0.04 Chisholm, CVD 1, 49 (1995) Ge(NEt₂)₄ >109 109/2  ChematCatalog, Northridge, CA Ge(NMe₂)₄ 14, liquid 203/760 Abel, J. Chem. Soc.1961, 4933; Chemat Ge(N^(t)Bu₂)₂ 2, liquid Lappert, J. Chem. Soc., Chem.Com. 13, 621(1980) Ge(N^(t)BuSiMe₃)₂ 22   50/0.04 Lappert, J. Chem. Soc,Dalton Trans. 1977, 2004 Ge(TMPD)₂ 60-62   70/0.02 Lappert, J. Chem.Soc., Chem. Com. 13, 621(1980) Hf(NEt₂)₄ liquid  100/0.84 Bradley, J.Chem. Soc A, 1969, 980 Hf(NEtMe)₄ liquid   83/0.05 Becker & Gordon,2000; Aldrich Hf(NMe₂)₄ 30   70/0.73 Bradley, J. Chem. Soc. A, 1969, 980Hg(N(SiMe₃)₂)₂ liquid Earborn, J. Chem. Soc, Chem. Comm., 1051 (1968)Ho(N(SiMe₃)₂)₃ 161-164 80-85/10⁻⁴ Bradley, J. Chem. Soc, Dalton 1973,1021 In(N(SiMe₃)₂)₃ 168 Wannagat, J. Organomet. Chem. 33, 1 (1971)In(TMPD)₃ Frey et al., Z. Anorg. Allg. Chem. 622, 1060 (1996)KN(SiHexMe₂)₂ liquid Broomhall-Dillard, Mater. Res. Soc. 606, 139 (2000)KN(SiMe₃)₂ 90-100/10⁻³ Fieser & Fieser 4, 407 La(N(SiMe₃)₂)₃ 145-149100/10⁻⁴ Bradley, J. Chem. Soc, Dalton 1973, 1021 La(N^(t)BuSiMe₃)₃146-147 90-95/10⁻⁴ Becker, Suh & Gordon, 2000 La(N^(i)Pr₂)₃ Aspinall, J.Chem. Soc, Dalton 1993, 993 La(TMPD)₃ 137-139 100/10⁻⁴ Suh & Gordon,2000 LiN(SiEtMe₂)₂ liquid 123/0.2  Broomhall-Dillard, Mater. Res. Soc.606, 139 (2000) LiN(SiMe₃)₂ 71-72 115/1  Inorg. Synth. 8, 19 (1966)Li(TMPD) Kopka, J. Org. Chem. 52, 448 (1987) Lu(N(SiMe₃)₂)₃ 167-17075-80/10⁻⁴ Bradley, Chem. Comm. 1972, 349 Mg(N(SiMe₃)₂)₂ 123 Andersen,J. Chem. Soc, Dalton Trans. 1982, 887 Mg(TMPD)₂ Eaton, JACS 111, 8016(1989) Mn(N(SiBuMe₂)₂)₂ liquid  143/0.06 Broomhall-Dillard & Gordon,1999 Mn(N(SiMe₃)₂)₂ 55-60 112-120/0.2 Bradley, Trans. Met. Chem. 3, 253(1978) Mn(N(SiMe₃)₂)₃ 108-110 Power, JACS 11, 8044 (1989)Mo(N^(t)BuSiMe₃)₃ Laplaza, Cummins, JACS 118, 8623 (1996) Mo₂(NEt₂)₆Chisholm, JACS 98, 4469 (1976) Mo₂(NMe₂)₆ solid 100/10⁻⁴ Chisholm, JACS98, 4469 (1976) Mo(NEt₂)₄ liquid 80-110/10⁻⁴ Bradley & Chisholm, J.Chem. Soc. A 1971, 2741 Mo(NMe₂)₄ solid 40-70/0.1 Bradley & Chisholm, J.Chem. Soc. A 1971, 2741 NaN(Si^(n)BuMe₂)₂ liquid  189/0.08Broomhall-Dillard, Mater. Res. Soc. 606, 139 (2000) NaN(SiMe₃)₂ 171-175170/2  Chem. Ber. 94, 1540 (1961) Nb(N(SiMe₃)₂)₃ solid Broomhall-Dillard& Gordon, 1998 Nb(NEt₂)₄ liquid Bradley & Thomas, Can. J. Chem. 40, 449(1962) Nb(NEt₂)₅ >120 120/0.1  Bradley & Thomas, Can. J. Chem. 40, 449(1962) Nb(NMe₂)₅ >100 100/0.1  Bradley & Thomas, Can. J. Chem. 40, 449(1962) Nd(N(SiMe₃)₂)₃ 161-164 85-90/10⁻⁴ Bradley, J. Chem. Soc, Dalton1973, 1021 Nd(N^(i)Pr₂)₃ Bradley, Inorg. Nucl. Chem. Lett. 12, 735(1976)Ni(N(SiMe₃)₂)₂ liquid  80/0.2 Burger & Wannagat, Mh. Chem. 95, 1099(1964) Pb(N(SiMe₃)₂)₂ 39   60/0.04 Lappert, J. Chem. Soc, Chem. Com. 16,776 (1980) Pb(N^(t)BuSiMe₃)₂ 22   50/0.04 Lappert, J. Chem. Soc, DaltonTrans. 1977, 2004 Pr(N(SiMe₃)₂)₃ 155-158 88-90/10⁻⁴ Bradley, Chem. Comm.1972, 349 Sb(NMe₂)₃ liquid  50/0.5 Cowley, JACS 95, 6506 (1973)Sb(N(Me)(SiMe₃))₃  9-11 78-79/0.1 Birkofer & Ritter, Chem. Ber. 93, 424(1960) Sc(N(SiMe₃)₂)₃ 172-174 Bradley, J. Chem. Soc, Dalton 1972, 1580SiH₂(NMe₂)₂ −104  93/760 Anderson et al., J. Chem. Soc. Dalton 12, 3061(1987) SiH(NMe₂)₃ −90 62/45 Gelest, Pfaltz & Bauer, Strem CatalogsSi(NMe₂)₄ 1-2 196/760 Gordon, Hoffman & Riaz, Chem. Mater. 2, 480 (1990)Si(NHMe)₄ 37   45/0.05 Schmisbaur, Inorg. Chem. 37, 510 (1998)Si(NHn-Pr)₄ liquid   75/0.05 Schmisbaur, Inorg. Chem. 37, 510 (1998)Si(NEt₂)₄ 3-4 74/19 Abel et al., J. Chem. Soc. 1965, 62; Chemat Si(NCO)₄25-26 40/1  Forbes & Anderson, JACS 62, 761 (1940); Gelest, Petrarch,Showa-Denko Si(NCO)₄ 25-26 40/1  Forbes & Anderson, JACS 62, 761 (1940);Gelest, Petrarch, Showa-Denko Sm(N(SiMe₃)₂)₃ 155-158 83-84/10⁻⁴ Bradley,Chem. Comm. 1972, 349 Sn(N(SiMe₃)₂)₂ 38   84/0.04 Chisholm, CVD 1, 49(1995) Sn(NEt₂)₄ liquid   90/0.05 Jones & Lappert, J. Chem. Soc. 1965,1944 Sn(NMe₂)₄ liquid   51/0.15 Jones & Lappert, J. Chem. Soc. 1965,1944 Sn(N^(t)Bu₂)₂ 47 Lappert, J. Chem. Soc, Chem. Com. 13, 621(1980)Sn(N^(t)Bu₂)₃ Hudson, J. Chem. Soc. Dalton Trans. 1976, 2369Sn(N^(t)BuSiMe₃)₂ 19, liquid   50/0.04 Lappert, J. Chem. Soc, DaltonTrans. 1977, 2004 Sn(N^(t)BuSiMe₃)₃ Hudson, J. Chem. Soc. Dalton Trans.1976, 2369 Sn(TMPD)₂ Lappert, J. Chem. Soc, Chem. Com. 16, 776 (1980)Sr(N(SiMe₃)₂)₂ 164 Westerhauser, Inorg. Chem. 30, 96 (1991) Ta(NEt₂)₄120/0.1  Bradley & Thomas, Can. J. Chem. 40, 1355 (1962) Ta(NMe₂)₅ >180100/0.1  Bradley & Thomas, Can. J. Chem. 40, 1355(1962); StremTa(N^(t)Bu)(NEt₂)₃ liquid  90/0.1 Inorgtech Ta(NEt)(NEt₂)₃ liquid120/0.1  Becke-Goehring & Wunsch, Chem. Ber. 93, 326 (1960)Tb(N(SiMe₃)₂)₃ 162-165 78-82/10⁻⁴ Wolczanski, Inorg. Chem. 31, 1311(1992) Th(NEt₂)₄ 40-50/10⁻⁴ Reynolds & Edelstein, Inorg. Chem. 16, 2822(1977) Th(NPr₂)₄ liquid 60-70/10⁻⁴ Reynolds & Edelstein, Inorg. Chem.16, 2822 (1977) Ti(N(SiMe₃)₂)₃ solid Bradley, J. Chem. Soc, Dalton 1972,1580 Ti(NEt₂)₄ liquid 112/0.1  Bradley & Thomas, J. Chem. Soc. 1960,3857 Ti(N^(i)Pr₂)₃ Kruse, Inorg. Chem. 9, 2615 (1970) Ti(N^(i)Pr₂)₄82-85   110/0.001 Froneman, P, S, Si, Relat. Elem. 47, 273 (1990)Ti(NMe₂)₄ liquid   50/0.05 Bradley & Thomas, J. Chem. Soc 1960, 3857Tl(N(SiMe₃)₂)₃ Allman, J. Organomet. Chem. 162, 283 (1978) U(N(SiMe₃)₂)₃137-140 80-100/10⁻³ Andersen, Inorg. Chem. 18, 1507 (1979) U(NEt₂)₄115-125/.06 Jones, JACS 78, 4285 (1956) U(NPr₂)₄ liquid 40-50/10⁻⁴Reynolds & Edelstein, Inorg. Chem. 16, 2822 (1977) V(N(SiMe₃)₂)₃ >95  95/0.005 Bradley, J. Chem. Soc, Dalton 1972, 1580 V(NEt₂)₄ liquid  90/0.001 Bradley, Chem. Commun. 1964, 1064 V(NMe₂)₄ solid   50/0.001Bradley, J. Chem. Soc A, 1969, 2330 V(O)(NMe₂)₃ 40   40/0.001 Davidson,Harris & Lappert, JCS Dalton 1976, 2268 W₂(NEt₂)₆ solid 140-170/10⁻⁴Chisholm, JACS 97, 5626 (1975); 98, 4477 (1976) W₂(NMeEt)₆ solid100-130/10⁻⁴ Burger & Wannagat, Monatsh. 95, 1099 (1964) W₂(NMe₂)₆ solid100-120/10⁻⁴ Burger & Wannagat, Monatsh. 95, 1099 (1964)W(N^(t)Bu)₂(NH^(t)Bu)₂ 89-90 60-65/10⁻⁴ Nugent & Harlow, Inorg. Chem.19, 777 (1980) W(N^(t)Bu)₂(NEtMe)₂ liquid  87/0.1 Suh & Gordon, 2000W(N^(t)Bu)₂(NMe₂)₂ liquid  75/0.1 Suh & Gordon, 2000 Y(N(SiMe₃)₂)₃180-184 100/10⁻⁴ Bradley, J. Chem. Soc, Dalton 1973, 1021; AlfaY(N^(i)Pr₂)₃ Bradley, Inorg. Nucl. Chem. Lett. 12, 735(1976)Y(N^(t)BuSiMe₃)₃ 158-160 90-95/10⁻⁴ Suh & Gordon, 2000 Y(TMPD)₃ 177-179100/10⁻⁴ Suh & Gordon, 2000 Yb(N(SiMe₃)₂)₃ 162-165 Bradley, J. Chem.Soc, Dalton 1973, 1021 Yb(N¹Pr₂)₃ Bradley, Inorg. Nucl. Chem. Lett. 12,735 (1976) Zn(N(SiMe₃)₂)₂ liquid 120/0.1  Inorg. Chem. 23, 1972 (1984)Zn(N^(t)Bu₂)₂ Schumann, Z. Anorg. Allg. Chem. 623, 1881 (1997) Zn(TMPD)₂Schumann, Z. Anorg. Allg. Chem. 623, 1881 (1997) Zr(NEt₂)₄ liquid112/0.1  Bradley & Thomas, J. Chem. Soc. 1960, 3857 Zr(NEtMe)₄ liquid  82/0.05 Becker & Gordon, 2000 Zr(N^(i)Pr₂)₄ >120   120/0.001 Bradley,Inorg. Nucl. Chem. Lett. 11, 155 (1975) Zr(NMe₂)₄ 70 65-80/0.1 Bradley &Thomas, J. Chem. Soc. 1960, 3857In Table 1, TMPD stands for 2,2,6,6-tetramethylpiperidide. Furtherexamples may be found in the book Metal and Metalloid Amides, by M. F.Lappert, P. P. Power, A. R. Sanger and R. C. Srivastava, published in1980 by Ellis Horwood Ltd., a division of John Wiley & Sons.

In at least some embodiments, metal alkyls are useful in the practice ofthis invention. Some examples are given in Table 2, as well as acommercial source or literature reference of their synthesis.

TABLE 2 Some Volatile Organometallic Compounds Melt. Pt. Vapor Press.Compound ° C. ° C./Torr Sources AlMe₃ 15.4 20/8  Strem Ba(n-PrMe₄Cp)₂liquid Strem Ba(^(i)Pr₄Cp)₂ 149-150   90/0.01 J. Am. Chem. Soc. 113,4843-4851 (1991) Ba(Me₅Cp)₂ 265-268  140/0.01 J. Organomet. Chem. 325,31-37 (1987) BeEt₂ 12, liquid 110/15  Strem BiMe₃ liquid 110/760 Pfaltz& Bauer, Organometallics Ca(^(i)Pr₄Cp)₂ 196-200  190/0.01 J. Am. Chem.Soc. 113, 4843-4851 (1991) Ca(Me₅Cp)₂ 207-210   90/0.01 J. Organomet.Chem. 325, 31-37 (1987) CdMe₂ −4.5 105.5/760   Strem CeCp₃ 452 230/0.01Strem Ce(^(i)PrCp)₃ Strem Ce(Me₄Cp)₃ solid Aldrich CoCp₂ 176-180Aldrich, Strem CoCp(CO)₂ liquid 37-38.5/2 Strem Co(CO)₃NO liquid  50/760Strem CrCp₂ 168-170 Aldrich, Strem Cr(Me₅Cp)₂ 200 Strem Cr(^(i)PrCp)₂solid Strem Cr(EtBz)₂ liquid 140-160/1 Strem CuCpPEt₃ solid   60/0.01Strem Er(Cp)₃ 285  200/0.01 Strem Er(^(i)PrCp)₃ 63-65 222/10  Aldrich,Alfa, Strem Er(BuCp)₃ liquid 240/0.1  Aldrich, Alfa (pyrophoric)Eu(Me₄Cp)₃ solid Aldrich FeCp(Me₂NCH₂Cp) liquid 91-92/0.5 StremFeCp(¹BuCp) liquid   80/0.15 Strem GaMe₃ −15, liquid 55.7/760  StremGdCp₃ 295 Aldrich, Alfa, Strem Gd(^(i)PrCp)₃ liquid  200/0.01 Erbil,U.S. Pat. No. 4,882,206 (1989) InCp₃ solid   50/0.01 Strem In(Me₅Cp)₃Strem InMe₃ 88 Strem Ir(MeCp)(1,5-COD) Strem La(¹PrCp)₃ liquid180-195/0.01 Strem; Erbil, U.S. Pat. No. 4,882,206 (1989) LaCp₃ 295 dec.218/0.1  Aldrich, Alfa, Strem LaCp₃(NCCH₃)₂ 162 Inorganica Chim. Acta100, 183-199 (1985) La(Me₂NC₂H₄Cp)₃ 75   160/0.001 J. Organomet. Chem.462, 163-174 (1993) Mg(PrCp)₂ liquid Strem Mg(EtCp)₂ liquid Aldrich,Strem MgCp₂ 180 160/0.1  Aldrich, Strem MnCp₂ 175 Aldrich, StremMn(EtCp)₂ liquid Aldrich (pyrophoric) Mn(Me₅Cp)₂ 292 Strem Mo(EtBz)₂liquid Strem NdCp₃ 417  220/0.01 Aldrich, Alfa, Strem Nd(^(i)PrCp)₃solid Aldrich, Alfa, Strem Ni(PF₃)₄ liquid 70.7/760  Strem PrCp₃ 427 220/0.01 Aldrich, Alfa, Strem Pr(^(i)PrCp)₃ 50-54 Aldrich, Alfa, StremSbEt₃ 156/760 Strem ScCp₃ 240  200/0.05 Aldrich, Strem SmCp₃ 356 220/0.01 Strem Sm(^(i)PrCp)₃ Zh. Neorg. Khim. 27, 2231-4 (1982)Sr(^(i)Pr₄Cp)₂ 151-153 Chem. Rev. 93, 1023-1-36 (1993) Sr(Me₅Cp)₂216-218 J. Organomet. Chem. 325, 31-37 (1987) solid Aldrich, Strem TmCp₃solid Strem Tm(^(i)PrCp)₃ MRS Symp. Proc. 301, 3-13 (1993) TICp solid 75/0.1 Strem VCp₂ 165-167 200/0.1  Aldrich, Strem V(EtCp)₂ liquidAldrich W(¹PrCp)₂H₂ liquid 122-125/0.1 Aldrich, Strem YCp₃ 296 200/2 Alfa, Strem Y(MeCp)₃ Strem Y(^(n)PrCp)₃ Strem Y(BuCp)₃ liquid Aldrich,Alfa, Strem YbCp₃ 277 150(vac.) Strem Yb(^(i)PrCp)₃ 47 Zh. Neorg. Khim.27, 2231-4 (1982) ZnEt₂ −28, liquid 124/760 Aldrich, Strem ZnMe₂ −42,liquid  46/760 Aldrich, Strem ZrCp₂Me₂ 170 Aldrich, StremZr(^(t)BuCp)₂Me₂ StremIn Table 2, Cp is an abbreviation for cyclopentadienide, Me₅ Cprepresents pentamethylcyclopentadienide, ^(i)PrCp representsisopropylcyclopentadienide, ^(i)PrMe₄ Cp stands forisopropyltetramethylcyclopentadienide, ^(i)Pr₄ Cp stands fortetraisopropylcyclopentadienide, EtCp stands for ethylcyclopentadienide,PrCp stands for propylcyclopentadienide, ^(i)PrCp stands forisopropylcyclopentadienide, BuCp stands for butylcyclopentadienide, Bzfor benzenide, EtBz for a mixture of isomers of ethylbenzenide and1,5-COD for 1,5-cyclooctadienide.

In at least some embodiments, metal or metalloid alkoxides can be usedin the practice of this invention. Suitable compounds are listed inTable 3, as well as a commercial source or a literature reference oftheir synthesis.

TABLE 3 Some Volatile Metal or Metalloid Alkoxides Melt. Pt. VaporPress. Compound ° C. ° C./Torr Sources Al₂Et₃(O-sec-Bu)₃ liquid 190/0.1 Strem B(OMe)₃ −29, 68.7/760  Aldrich, Rohm and liquid Haas, StremHf(O^(t)Bu)₄ liquid 90/5  Strem Nb(OEt)₅ 6, liquid  156/0.05 Aldrich,Chemat, Strem Ta(OEt)₅ 21  146/0.15 Aldrich, Chemat, Strem Ti(O^(i)Pr)₄20 58/1  Aldrich, Chemat, DuPont, Strem Y(OCMe₂CH₂NMe₂)₃ liquid  80/0.001 Herrmann, Inorg. Chem. 36, 3545-3552 (1997) Zr(O^(t)Bu)₄liquid 81/3, 90/5 Aldrich, StremMetal halides may also be used in the practice of this invention, butthey have the disadvantages that they tend to leave some halide impurityin the film and cause corrosion of substrates or apparatus.4. Reactions with Water and Alcohols.

In at least some embodiments, part of the silanol or phosphate isreplaced with water in order to deposit metal-rich silicates andphosphates. In a CVD reactor, water vapor tends to react very quicklywith the vapors of the metal precursors near the vapor entrance toproduce powder, rather than film on the substrate. In an ALD reactorsuch premature reactions are avoided because the reactants areintroduced alternately into the reactor, so reactions near the entranceare prevented and reaction is confined to the surface of the substrate.However, water tends to adsorb strongly on surfaces, so it can take along time to purge the ALD reactor between pulses of the reactants.

Alcohols such as isopropanol and tert-butanol can alleviate theseproblems with water, since the reactions of alcohols with metalcompounds are slower, and the more volatile alcohols can be pumped morequickly from an ALD reactor. Alcohols such as isopropanol andtert-butanol are particularly appropriate for reactions involvingthermally liable metal compounds. In some cases the substratetemperature is raised in order to decompose alkyl alcohols and therebyremove their carbon content from the film. A thermally labile metalcompound may self-decompose at higher substrate temperatures, soself-limiting ALD reactions cannot be achieved.

The arene hydrates are a class of alcohols that decompose at lowertemperatures than ordinary alkyl alcohols, and thus can be used toprovide carbon-free metal oxides at low enough temperatures to avoidself-decomposition of even thermally labile metal compounds. Forexample, benzene hydrate decomposes easily to water and benzene becauseof the aromatic stabilization of the benzene byproduct:

Other examples of useful arene hydrates are alkyl-substituted benzenehydrates such as the various isomers of toluene hydrate:

Other useful alcohols include the two naphthalene hydrates

and alkyl-substituted naphthalene hydrates such as methyl naphthalenehydrate. Thus arene alcohols may be used in the reaction of metalcompounds at moderate deposition conditions. In particular, it can beused for the formation of metal oxides, or for the formation of metalsilicates or metal phophates when used in combination with the siliconand phosphorus precursors described herein.

In at least some embodiments of the present invention, a metal oxide isobtained by reaction of a metal amide with water. Suitable metal amidesinclude any of those listed in Table 1. Thus, by way of example, hafniumoxide was prepared by ALD using water vapor andtetrakis(dimethylamido)hafnium. This ALD reaction was found to besurprisingly efficient, in that almost all of the precursor that wasdelivered into the reaction chamber was deposited as film on thesubstrate and on the exposed wall of the chamber. It was also found tobe surprisingly fast, going to completion (saturation of the surfacereaction on a flat surface) with less than 50 Langmuirs of vapor flux (1Langmuir is the flux delivered to a surface in one second by a partialpressure of 10⁻⁶ Torr of the precursor). The byproducts of the reactionwere found to consist of dimethylamine vapor, which does not etch thedeposited hafnium oxide film. Most surprisingly, the use oftetrakis(alkylamido)hafnium precursors succeeded in the ALD of highlyuniform films of hafnium oxide even in holes with very high aspectrations (over 40). By way of contrast, the reactants commonly used inthe prior art for ALD of hafnium oxide, HfCl₄ and Hf(O-tert-Bu)₄, havenot succeeded in the uniform deposition of HfO₂ in holes with such highaspect ratios.

Vaporization of Reactants and Product Deposition.

Vapors of liquid precursors may be formed by conventional methods,including heating in a bubbler, in a thin-film evaporator, or bynebulization into a carrier gas preheated to about 100 to 250° C. Thenebulization may be carried out pneumatically or ultrasonically. Solidprecursors may be dissolved in organic solvents, including hydrocarbonssuch as decane, dodecane, tetradecane, toluene, xylene and mesitylene,and with ethers, esters, ketones and chlorinated hydrocarbons. Solutionsof liquid precursors generally have lower viscosities than the pureliquids, so that in some cases it may be preferable to nebulize andevaporate solutions rather than the pure liquids. The liquids orsolutions can also be evaporated with thin-film evaporators or by directinjection of the liquids into a heated zone. Thin-film evaporators aremade by Artisan Industries (Waltham, Mass.). Commercial equipment fordirect vaporization of liquids is made by MKS Instruments (Andover,Mass.), ATMI, Inc. (Danbury, Conn.), Novellus Systems, Inc. (San Jose,Calif.) and COVA Technologies (Colorado Springs, Colo.). Ultrasonicnebulizers are made by Sonotek Corporation (Milton, N.Y.) and CetacTechnologies (Omaha, Nebr.).

The silicon precursors of the present invention may be reacted withmetal or metalloid amides, such as those in Table 1, to form metal ormetalloid silicates. The silicon precursors of the present invention maybe reacted with organometallic compounds, such as those in Table 2, toform metal silicates. The silicon precursors of the present inventionmay be reacted with metal or metalloid alkoxides, such as those in Table3, to form metal or metalloid silicates. The silicon precursors of thepresent invention may also be reacted with other suitably reactive metalcompounds to form metal silicates. For example, tris(tert-butoxy)silanolmay be reacted with tris(tert-butyl(trimethylsilyl)amido)yttrium(Table 1) to form yttrium silicate (Examples 5 and 6). Also,tris(tert-butoxy)silanol may be reacted withtris(tert-butyl(trimethylsilyl)amido)lanthanum (Table 1) to formlanthanum silicate (Examples 7 and 8). Metal oxides may be obtained byreactin of a suitable metal and with water.Tris(bis(trimethylsilyl)amido)lanthanum reacts with water vapor to forma more lanthanum-rich silicate (Example 21). Lanthanum oxide may bedeposited from silicon-free precursors such astris(2,2,6,6-tetramethylpiperidido)lanthanum (Example 22).

The phosphorus precursors of the present invention may be reacted withsuitably reactive metal compounds, such as those in the Tables, to formmetal phosphates. For example, diisopropylphosphate may be reacted withlithium bis(ethyldimethylsilyl)amide (Table 1) to provide a process fordepositing lithium phosphate films that are lithium ion conductors, asis shown in Examples 9 and 10.

The process of the invention can be carried out in standard equipmentwell known in the art of chemical vapor deposition (CVD). The CVDapparatus brings the vapors of the reactants into contact with a heatedsubstrate on which the material deposits. A CVD process can operate at avariety of pressures, including in particular normal atmosphericpressure, and also lower pressures. Commercial atmospheric pressure CVDfurnaces are made in the USA by the Watkins-Johnson Company (ScottsValley, Calif.), BTU International (North Billerica, Mass.) andSierraTherm (Watsonville, Calif.). Commercial atmospheric pressure CVDequipment for coating glass on the float production line is made in theUSA by Pilkington North America (Toledo, Ohio), PPG Industries(Pittsburgh, Pa.) and AFG Industries (Kingsport, Tenn.). Low-pressureCVD equipment is made by Applied Materials (Santa Clara, Calif.), SpireCorporation (Bedford, Mass.), Materials Research Corporation (Gilbert,Ariz.), Novellus Systems, Inc. (San Jose, Calif.), Genus (Sunneyvale,Calif.), Mattson Technology (Frement, Calif.), Emcore Corporation(Somerset, N.J.), NZ Applied Technologies (Woburn, Mass.), COVATechnologies (Colorado Springs, Colo.) and CVC Corporation (Freemont,Calif.). Apparatus adapted to atomic layer deposition (ALD) is availablefrom Genus (Sunneyvale, Calif.) and ASM Microchemistry (Espoo, Finland).

The process of the invention may also be carried out using atomic layerdeposition (ALD). ALD introduces a metered amount of a first reactantcomponent into a deposition chamber having a substrate therein for layerdeposition. A thin layer of the first reactant is deposited on thesubstrate. After a preselected time period, a metered amount of a secondreactant component is then introduced into the deposition chamber, whichis deposited on and interacts with the already deposited layer of thefirst reactant component. Alternating layers of first and secondreactant components are introduced into the deposition chamber anddeposited on the substrate to form a layer of controlled composition andthickness. Alternation of deposition may be on the order of seconds tominutes and is selected to provide adequate time for the just introducedcomponent to deposit on the substrate and for any excess vapor to beremoved from the headspace above the substrate. It has been determinedthat the surface reactions are self-limiting so that a reproduciblelayer of predictable composition is deposited. Use of more than tworeactant components is within the scope of the invention.

In at least some embodiments of the invention, automobile fuel injectors(Ford model CM-4722 F13Z-9F593-A) may be used to deliver pulses of thesolutions of precursors into the nitrogen carrier gas. Solution isdelivered each time a valve opens for about 50 milliseconds.

In another embodiment of the invention, 6-port sampling valves (Valcomodel EP4C6WEPH, Valco Instruments, Houston, Tex.) normally used forinjecting samples into gas chromatographs may be used to deliver pulsesof solutions into a suitable carrier gas. Each time that a valve isopened, solution flows into a tube in which solution is vaporized byheat from hot oil flowing over the outside of the tube. Carrier gasmoves the vapor from the tube into the ADD reactor tube.

In at least some embodiments, a layer is deposited by ALD using anapparatus such as that illustrated in FIG. 1. According to at least someembodiments, measured doses of reactant vapor 30 are introduced into theheated deposition chamber 110 by the use of a pair of air-actuateddiaphragm valves, 50 and 70 (Titan II model made by Parker-Hannifin,Richmond Calif.). The valves are connected by a chamber 60 having ameasured volume V, and this assembly is placed inside an oven 80 held ata controlled temperature T₂. The pressure of the reactant vapor 30 inthe precursor reservoir 10 is equal to the equilibrium vapor pressureP_(eq) of the solid or liquid reactant 20 at a temperature T₁ determinedby the surrounding oven 40. The temperature T₁ is chosen to be highenough so that the precursor pressure P_(eq) is higher than the pressureP_(dep) in the deposition chamber. The temperature T₂ is chosen to behigher than T₁ so that only vapor and no condensed phase is present inthe valves 50 and 70 or the chamber 60. In the case of a gaseousreactant, its pressure can be set by a pressure regulator (not shown)that reduces its pressure from the pressure in the precursor gascylinder 10.

A similar arrangement is provided for each reactive precursor introducedinto the deposition chamber 110. Thus, a precursor reservoir 11 holds asolid or liquid reactant 21 having a vapor pressure 31 at a temperatureT₁′ maintained by surrounding oven 41. Valves 51 and 71 are connected bya chamber 61 having a measured volume V′ and this assembly is housed inoven 81 at temperature T₂′.

Carrier gas (such as nitrogen) flows at a controlled rate into inlet 90in order to speed the flow of the reactants into the deposition chamberand the purging of reaction byproducts and un-reacted reactant vapor. Astatic mixer may be placed in the tubing 100 leading into the reactor,to provide a more uniform concentration of the precursor vapor in thecarrier gas as it enters the deposition chamber 110 heated by furnace120 and containing one or more substrates 130. The reaction byproductsand un-reacted reactant vapors are removed by trap 140 before passinginto a vacuum pump 150. Carrier gas exits from exhaust 160.

In operation, valve 70 is opened so that the pressure inside chamber 60is reduced to a value P_(dep) close to that of the deposition chamber110. Then valve 70 is closed and valve 50 is opened to admit precursorvapor from precursor reservoir 10 into chamber 60. Then valve 50 isclosed so that the volume V of chamber 60 contains vapor of theprecursor at a pressure P_(eq). Finally, valve 70 is opened to admitmost of the precursor vapor contained in chamber 60 into the depositionchamber. The number of moles, n, of precursor delivered by this cyclecan be estimated by assuming that the vapor obeys the ideal gas law:n=(P _(eq) −P _(dep))(V/RT ₁)  (14)where R is the gas constant. This expression also assumes that carriergas from tube 90 does not enter chamber 60 through valve 70 during thebrief time that it is open to release the precursor vapor. If mixing ofcarrier gas with the precursor vapor does occur during the time thatvalve 70 is open, then a larger dose of precursor vapor may bedelivered, up to a maximum valuen=(P _(eq))(V/RT ₁)  (15)if all the residual precursor vapor in chamber 60 is displaced bycarrier gas. For precursors with relatively high vapor pressure(P_(eq)>>P_(dep)), there is not much difference between these twoestimates of the precursor dose.

This cycle of delivering precursor 20 is repeated if necessary until therequired dose of precursor 20 has been delivered into reaction chamber.Normally, in an ALD process, the dose of precursor 20 delivered by thiscycle (or several such cycles repeated to give a larger dose) is chosento be large enough to cause the surface reactions to go to completion(also called “saturation”).

Next a dose of vapor 31 from a second precursor 21 may be measured anddelivered by a similar apparatus with components numbered similarly tothe apparatus for the first precursor 20.

In the case of precursors with vapor pressure so low that P_(eq) is lessthan P_(dep), this method will not deliver any precursor vapor into thedeposition chamber. The vapor pressure can be increased by raising thetemperature T₁, but in some cases a higher temperature would result inthermal decomposition of the precursor. In such cases of thermallysensitive precursors with low vapor pressure, vapor may be deliveredusing the apparatus in FIG. 2. The chamber 220 is first pressurized withcarrier gas delivered through tube 240 and valve 200 from a pressurecontroller (not shown). Valve 200 is then closed and valve 210 opened toallow the carrier gas to pressurize precursor reservoir 220 to pressureP_(tot). The mole fraction of precursor vapor in the vapor space 30 ofreservoir 10 is then P_(eq)/P_(tot). If P_(tot) is set to a pressurelarger than the pressure P_(dep) in the deposition chamber, then thenumber of moles delivered in a dose can be estimated from the equationn=(P _(eq) /P _(tot))(P _(tot) −P _(dep))(V/RT ₁),  (16)where V is the volume of the vapor space 30 in chamber 10. This dose isdelivered by opening valve 230. If carrier gas from tube 90 enters thevolume 30 during the time that the valve 230 is open, then a dosesomewhat larger than this estimate may be delivered. By making thevolume V large enough, a precursor dose that is certainly large enoughto saturate the surface reaction may be delivered. If the vapor pressureP_(eq) is so low that the required volume V would be impracticablylarge, then additional doses from volume V may be delivered beforedelivering a dose of the other reactant.

A similar apparatus is provided for each precursor reactant of thesystem. Thus, chamber 221 is first pressurized with carrier gasdelivered through tube 241 and valve 201 from a pressure controller (notshown). Valve 201 is then closed and valve 211 is opened to allow thecarrier gas to pressurize precursor reservoir 11 to pressure P_(tot).This dose is delivered by opening valve 231. Carrier gas from tube 91promotes transport of the metered dose to the deposition chamber.

In an isothermal deposition zone, material is generally deposited on allsurfaces exposed to the precursor vapors, including substrates and theinterior chamber walls. Thus it is appropriate to report the precursordoses used in terms of moles per unit area of the substrates and exposedchamber walls.

The liquids and solutions described herein may also be used asmetal-containing precursors for other types of deposition processes,such as spray coating, spin coating or sol-gel formation of mixed metaloxides. The high solubility and miscibility of these precursors is anadvantage in forming the required solutions.

The amides disclosed in these examples appeared to be non-pyrophoric bythe methods published by the United States Department of Transportation.One test calls for placing about 5 milliliters of the material on annon-flammable porous solid, and observing that no spontaneous combustionoccurs. Another test involves dropping 0.5 milliliters of the liquid orsolution on a Whatman No. 3 filter paper, and observing that no flame orcharring of the paper occurs.

The precursors generally react with moisture in the ambient air, andshould be stored under an inert, dry atmosphere such as pure nitrogengas.

The invention may be understood with reference to the following exampleswhich are for the purpose of illustration only and which are notlimiting of the invention, the full scope of which is set forth in theclaims which follow.

Example 1 CVD of Zirconium Silicate

A solution (1% by weight) of tris(tert-butoxy)silanol in mesitylene waspumped at a rate of 6 ml/hour into a 1/16″ O.D. tee joint through whichnitrogen gas flowed at 0.4 L/min. The resulting fog flowed into a tubeheated to 250° C. A solution (1% by weight) oftetrakis(ethylmethylamido)zirconium in mesitylene was pumped at a rateof 12 ml/hour into another tee joint through which nitrogen gas flowedat 0.4 L/min. The resulting fog flowed into the same heated tube. Thegas pressure was maintained at 5 Torr by a vacuum pump attached to theoutlet of the glass tube by a liquid nitrogen trap. Substrates ofsilicon and glassy carbon placed inside the tube were coated with a filmof zirconium silicate whose thickness varied along the length of thetube. Analysis of the film by Rutherford backscattering spectroscopygave a composition ZrSi₂O₆ for films deposited on glassy carbon. Nocarbon or nitrogen was detected in the film. The refractive indexes offilms deposited on silicon were found to be about 1.6 by ellipsometry.

Example 2 ALD of Zirconium Silicate

Example 1 was repeated except that the precursors were injected inalternate pulses spaced 5 seconds apart, instead of continuously. A filmof similar composition, ZrSi₂O₆, was deposited with uniform thicknessalong the whole length of the heated zone. The thickness was about 0.3nm per cycle.

Example 3 CVD of Hafnium Silicate

Example 1 was repeated with tetrakis(ethylmethylamido)hafnium in placeof tetrakis(ethylmethylamido)zirconium. Films of compositionapproximately HfSi₂O₆ were formed. No carbon or nitrogen was detected inthe film. The refractive indexes of films deposited on silicon werefound to be about 1.6 by ellipsometry.

Example 4 ALD of Hafnium Silicate

Example 3 was repeated except that the precursors were injected inalternate pulses spaced 5 seconds apart, instead of continuously. A filmof similar composition, HfSi₂O₆, was deposited with uniform thicknessalong the whole length of the heated zone. The thickness was about 0.3nm per cycle.

Example 5 CVD of Yttrium Silicate

Example 1 was repeated with tris(tert-butyl(trimethylsilyl)amido)yttriumin place of tetrakis(ethylmethylamido)zirconium. Films of compositionapproximately Y₂Si₂O₇ were formed. No carbon or nitrogen was detected inthe film. The refractive indexes of films deposited on silicon werefound to be about 1.6 by ellipsometry.

Example 6 ALD of Yttrium Silicate

Example 5 was repeated except that the precursors were injected inalternate pulses spaced 5 seconds apart, instead of continuously. A filmof similar composition, Y₂Si₂O₇, was deposited with uniform thicknessalong the whole length of the heated zone. The thickness was about 0.3nm per cycle. Composition approximately Y₂Si₂O₇.

Example 7 CVD of Lanthanum Silicate

Example 1 was repeated with tris(bis(trimethylsilyl)amido)lanthanum inplace of tetrakis(ethylmethylamido)zirconium and tetradecane in place ofmesitylene. Films with a La:Si ratio of about 0.9 were formed on aglassy carbon substrate at a substrate temperature of 250° C. No carbonor nitrogen was detected in the films.

Example 8 ALD of Lanthanum Silicate

Example 7 was repeated except that the precursors were injected inalternate pulses spaced 5 seconds apart, instead of continuously. A filmof similar composition was deposited with uniform thickness along thewhole length of the heated zone.

Example 9 CVD of Lithium Phosphate

Liquid lithium bis(ethyldimethylsilyl)amide (1 part by weight) was mixedwith mesitylene (99 parts). The resulting solution was nebulized bypumping at a rate of 12 ml/hour into a tee joint into nitrogen gasflowing at 0.30 L/min into the deposition zone inside a tube (24 mminside diameter) in a furnace heated to 250° C. Simultaneously a 1%mesitylene solution of diisopropylphosphate was similarly nebulized intoanother nitrogen carrier gas stream flowing at 0.30 L/min into the sametube furnace. The gas pressure was maintained at 5 Torr by a vacuum pumpattached to the outlet of the glass tube by a liquid nitrogen trap. Athin film was deposited on a silicon substrate placed on the bottom ofthe glass tube, as well as on the inside of the tube. The thicknessprofile showed a peak near the gas entrance to the tube furnace. Thefilm was analyzed by X-ray photoelectron spectroscopy to containlithium, phosphorus and oxygen.

Example 10 ALD of Lithium Phosphate

Example 9 was repeated with the change that the materials wereintroduced in alternating pulses spaced 5 seconds apart in time. Asimilar lithium phosphate film was deposited, except that the thicknesswas nearly constant throughout the deposition zone.

Comparative Example 1 Control deposition with onlytris(tert-butoxy)silanol

Example 1 was repeated using only the silicon precursor and no zirconiumprecursor. No film was deposited.

Comparative Example 2 Control deposition with onlytetrakis(ethylmethylamido)zirconium

Example 1 was repeated using only the zirconium precursor and no siliconprecursor. No film was deposited.

Comparative Example 3 Control deposition with onlytetrakis(ethylmethylamido) hafnium

Example 3 was repeated using only the hafnium precursor and no siliconprecursor. No film was deposited.

Comparative Example 4 Control deposition with onlytris(tert-butyl(trimethylsilyl)amido)yttrium

Example 5 was repeated using only the yttrium precursor and no siliconprecursor. No film was deposited.

Comparative Example 5 Control deposition with onlytris(bis(trimethylsilyl)amido) lanthanum

Example 7 was repeated using only the lanthanum precursor and no siliconprecursor. No film was deposited.

Comparative Example 6 Control deposition with only diisopropylphosphate

Example 9 was repeated using only the phosphorus precursor and nolithium precursor. No film was deposited.

Comparative Example 7 Control deposition with only lithiumbis(ethyldimethylsilyl)amide

Example 9 was repeated using only the lithium precursor and nophosphorus precursor. No film was deposited.

Example 11 ADL formation of Metal Silicates and Phosphates

The ALD examples 2, 4, 6, 8 and 10 were repeated using automobile fuelinjectors (Ford model CM-4722 F13Z-9F593-A) to deliver pulses of thesolutions of precursors into the nitrogen carrier gas. About 0.05 m ofsolution was delivered each time that a valve was opened for about 50milliseconds. Similar results were obtained.

The ALD examples 2, 4, 6, 8 and 10 were repeated using a 6-port samplingvalves (Valco model EP4C6WEPH, Valco Instruments, Houston, Tex.)normally used for injecting samples into gas chromatographs to deliverpulses of tetradecane solutions into the nitrogen carrier gas. Externalsample loops having volumes of 50 microliters were used. Each time thata valve was opened, about 50 microliters of solution flowed into a 1/16″O. D., 0.040″ I. D. nickel tube in which the solution was vaporized byheat from hot oil flowing over the outside of the tube. Nitrogen carriergas moved the vapor from the small tube into the ALD reactor tube.Similar results were obtained.

In another series of examples, pulses of those precursors that areliquids at room temperature were delivered for ALD experiments similarto examples 2, 4, 6, 8 and 10 using 4-port sampling valves with small(0.5 microliter) internal sampling loops (Valco model EH2CI4WE.5PH,Valco Instruments, Houston, Tex.). Each time that a valve was opened,about 0.5 microliters of liquid flowed into a 1/16″ O. D., 0.040″ I. D.nickel tube in which the liquid was vaporized by heat from hot oilflowing over the outside of the tube. Nitrogen carrier gas moved thevapor from the small tube into the ALD reactor tube. Similar resultswere obtained.

Example 12 ALD of Hafnium Oxide

A hafnium oxide layer was deposited using the apparatus of FIG. 1. Dosesof 0.5×10⁻⁹ moles/cm² of tetrakis(dimethylamido)hafnium vapor and 4×10⁻⁹moles/cm² of water vapor were injected alternately every 5 seconds intoa deposition chamber held at 250° C. The chamber was also fed acontinuous flow of nitrogen carrier gas sufficient to maintain apressure of 0.15 Torr. The deposition chamber had a cross-sectional areaof 2.3 square centimeters in the plane perpendicular to the direction ofgas flow through the chamber. The outlet of the deposition chamber wasattached to a vacuum pump with capacity (195 liters/minute) sufficientto pump a volume equal to the deposition chamber in about 0.012 seconds.

As a result of these reaction conditions, a transparent, electricallyinsulating hafnium oxide film was deposited on substrates in thedeposition chamber and onto its inner walls. Its composition wasdetermined to be HfO₂ by Rutherford backscattering spectroscopy (RBS) ofa film on a glassy carbon substrate. No carbon or nitrogen was detected(<1 atomic percent). By ellipsometry, its thickness was determined to be0.1 nanometer/cycle and its refractive index 2.05. Combining data fromRBS and ellipsometry yielded a density of about 9. The thickness wasconstant over the whole deposition region, to within the estimatedmeasurement error of about 1%. Small-angle X-ray reflectivitymeasurements confirmed the thickness and gave a density of 9.23 g/cm³.X-ray reflectivity also showed that the films are very smooth, with rootmean square surface roughness about 0.4 nm for a film 43 nm thick.Scanning electron microscopy showed that films grown at 150° C. are evensmoother than the ones grown at 250° C.

Repeating Example 12 with higher doses of either reactant did notincrease the film thickness or change its properties. These results showthat the surface reactions are self-limiting. This conclusion wasconfirmed by placing inside the deposition chamber 110 a quartz crystalmicro-balance (not shown), which showed that the amount of massdeposited first increased and then reached a plateau as the size of eachdose was increased. As a result of these self-limiting surfacereactions, uniform films could be deposited inside holes with ratios oflength to diameter over 50. Uniformity of thickness inside these holeswas improved by increasing the dose to 10 times the minimum required forsaturation of the reactions on a flat surface without the holes.Reducing the capacity (speed) of the vacuum pump also helps to improvethe step coverage by reducing the linear velocity of the vapors throughthe deposition chamber, thereby increasing the time during which thevapors can diffuse down the holes, i.e. increasing the flux (Langmuirsof exposure). FIG. 3 shows a scanning micrograph of holes coated withhafnium oxide, cleaved to reveal their highly uniform thickness. Thehafnium oxide layer is the bright line outlining each of the narrowvertical holes in the silicon, which appears as a dark background. Atthe top of the micrograph is the upper surface of the silicon from whichthe holes were etched prior to the deposition of the hafnium oxide.

Repeating Example 12 with substrate temperatures in the range from 100°C. to 300° C. gave similar results. At temperatures above 300° C., thethickness increased with increasing the dose oftetrakis(dimethylamido)hafnium. This shows that the surface reaction isnot self-limiting at temperatures above 300° C., due to thermaldecomposition of tetrakis(dimethylamido)hafnium.

Example 13 ALD of Zirconium Oxide

Example 12 was repeated with tetrakis(dimethylamido)zirconium in placeof tetrakis(dimethylamido)hafnium. Films of zirconium dioxide withsimilar properties were deposited.

Example 14 ALD of Hafnium Oxide

Example 12 was repeated with tert-butanol vapor in place of water vapor.Films of hafnium dioxide with similar properties were deposited.

Example 15 ALD of Tantalum Oxide

Example 12 was repeated with ethylimidotris(diethylamido)tantalum vaporin place of tetrakis(dimethylamido)hafnium vapor. Transparent films ofTa₂O₅ were deposited. They have a refractive index of 2.2, and athickness of about 0.06 nm per cycle.

Example 16 ALD of Aluminum Phosphate

ALD was carried out using alternating doses of 3×10⁻⁹ moles/cm² of thevapors of trimethylaluminum and diisopropylphosphate at a substratetemperature of 400° C. Transparent aluminum phosphate films withapproximate composition Al₂P₄O₁₃ were deposited at a rate of 0.1 nm percycle. They had a refractive index of about 1.5.

Example 17 ALD of Aluminum Silicate

ALD was carried out using alternating doses of 3×10⁻⁹ moles/cm² oftrimethylaluminum vapor and 1.2×10⁻⁸ moles/cm² oftris(tert-butoxy)silanol vapor at a substrate temperature of 300° C.Transparent aluminum silicate films with approximate compositionAl₂Si₈O₁₉ were deposited at a remarkably high rate of 1 nm per cycle.They had a refractive index of about 1.48. The surfaces of the films arevery smooth; atomic force microscopy determined a root mean squareroughness of less than 0.8 nm for an aluminum silicate film 150 nmthick. The tensile stress in a film 2 micrometers thick on a silicasubstrate was measured to be about 0.2 giga-Pascals. A similar filmdeposited on single-crystalline silicon showed a smaller tensile stressof 0.03 giga-Pascals. A film 6 microns thick showed cracks anddelamination because of the tensile stress.

This tensile stress can be reduced, eliminated, or even reversed tocompressive stress by plasma treatment. The deposition is temporarilyhalted after a thin layer (such as 5 to 10 nm) has been deposited, aradio-frequency plasma (in a low-pressure gas such as O₂+argon) isapplied, and then the plasma power is stopped and the deposition isresumed. Multiple cycles of deposition and plasma treatment may be usedto build up thicker layers with tensile or compressive stress valuesadjusted to the requirements of particular applications, particularlythose requiring thicker films.

Example 18 ALD of Aluminum Silicate

ALD was carried out using alternating doses of 3×10⁻⁹ moles/cm² oftrimethylaluminum vapor and 3×10⁻⁸ moles/cm² of tris(tert-butoxy)silanolvapor at a substrate temperature 200° C. Transparent aluminum silicatefilms with approximate composition Al₂Si₁₆O₃₅ were deposited at aremarkably high rate of 2 nm per cycle. They had a refractive index ofabout 1.47.

Example 19 ALD of Aluminum Silicate

ALD was carried out with alternating doses of 3×10⁻⁹ moles/cm² oftris(dimethylamino)aluminum vapor and 3×10⁻⁸ moles/cm² oftris(tert-butoxy)silanol vapor at a substrate temperature 250° C. Analuminum silicate film was formed with thickness 0.1 nm/cycle and arefractive index of about 1.46.

Example 20 ALD of Aluminum Silicate

Example 19 was repeated with tris(tert-pentyloxy)silanol vapor in placeof the tris(tert-butoxy)silanol vapor. Similar results were obtained.

Example 21 ALP of Aluminum Silicate

Example 19 was repeated with a dose of water vapor between the doses oftris(dimethylamino)aluminum vapor and tris(tert-butoxy)silanol vapor. Asimilar film was obtained with very uniform thickness of 0.1 nm/cycle(±1%) along the direction of gas flow.

Example 22 ALD of Lanthanum Silicate

Example 12 was repeated with tris(bis(trimethylsilyl)amido)lanthanumvapor in place of tetrakis(dimethylamido)hafnium vapor and with theapparatus of FIG. 2, used as described herein above. Transparent oxidefilms with a La:Si ratio of about 2 were formed on substrates at asubstrate temperature of 250° C. No carbon or nitrogen was detected inthe films. They have a refractive index of 1.7, and a thickness of about0.1 nm per cycle.

Example 23 ALD of Lanthanum Oxide

ALD can be carried out with alternating doses oftris(2,2,6,6-tetramethylpiperidido)lanthanum vapor using the apparatusof FIG. 2 and water vapor to form lanthanum oxide films.

Example 24 ALD of Silicon Dioxide

ALD can be carried out with alternating doses of tetraisocyanatosilanevapor and tris(tert-butoxy)silanol vapor to form silicon dioxide films.Larger fluxes of exposure (>10⁻⁷ Langmuirs) are required for these lessreactive precursors.

Those skilled in the art will recognize or be able to ascertain using nomore than routine experimentation, many equivalents to the specificembodiments of the invention described specifically herein. Suchequivalents are intended to be encompassed in the scope of the followingclaims.

1. A process for making an insulator in a microelectronic device, theprocess comprising: introducing a first reactant component into adeposition chamber; introducing a second reactant component into thedeposition chamber; and alternately repeating introducing the firstreactant component and the second reactant component into the depositionchamber; wherein deposition of the first reactant component and thesecond reactant component are self-limiting; wherein said first reactantcomponent comprises a metal alkylamide; wherein said second reactantcomponent interacts with the deposited first reactant component to formthe insulator; and wherein said insulator comprises oxygen and the metalfrom the metal alkylamide.
 2. The process as in claim 1, wherein theinsulator insulates a gate or a capacitor.
 3. The process in claim 2,wherein the metal alkylamide is a hafnium dialkylamide.
 4. The processas in claim 3, wherein the hafnium dialkylamide istetrakis(ethylmethylamido)hafnium.
 5. The process as in claim 3, whereinthe hafnium dialkylamide is tetrakis(dimethylamido)hafnium.
 6. A processas in claim 3, wherein the hafnium dialkylamide istetrakis(diethylamido)hafnium.
 7. A process as in claim 2, wherein themetal alkylamide is a zirconium dialkylamide.
 8. A process as in claim7, wherein the zirconium dialkylamide istetrakis(ethylmethylamido)zirconium.
 9. A process as in claim 7, whereinthe zirconium dialkylamide is tetrakis(dimethylamido)zirconium.
 10. Aprocess as in claim 7, wherein the zirconium dialkylamide istetrakis(diethylamido)zirconium.